1. Field of the Invention
The present invention relates to an improved float valve of the type used in hydrocarbon recovery operations with oilfield tubular materials in downhole operations. More particularly this invention relates to a float valve which can be used in either vertical or horizontal well bores and provides smooth functionality in the transition between vertical or horizontal well bores and improved life of the float valve. The invention further relates to the ease of the float valve assembly for all its parts and for precise and exact tolerance relationships for all its parts when assembled. The invention provides improved fluid flow through the float valve and sealing relationship by providing functionally improved angles between its seating surfaces. Also this invention provides improved fluid flow through the float valve by improved configurations of the axial stem of the valve member movably mounted in the float valve. This invention also provides surfaces and landing sites on the float valve for technology associated with sub joint strainers, spiders or X-collar filters to be used in cooperation with the float valve for improved performance.
2. Background of the Invention
Float valves have long been used in oilfield drilling operations with drilling fluids for drilling oil and gas wells. However over time, improvements have been made to drilling operations which include lateral wells, as well as vertical wells, and ever more exotic drilling fluids, gels and even high pressure air had been put into use. The new drilling fluids pass through the drill string like the older drilling fluids, and through the float valve but create new and enhanced stress and wear on the float valves, especially in lateral wells. In the case of high pressure air drilling operations for example, a float valve may open and close in excess of a hundred times per minute thereby exerting excessive forces on the moving valve member parts. Also new components have been developed for drilling fluid such as glass or other kinds of beads which are very fine, but abrasive, and can stick between moving parts of a float valve. Further lateral wells put the float valve and drilling head into a different gravitational alignment than vertical drilling which can cause wear and alignment problems with moving parts of a float valve.
The float valve is generally installed in a tubular string for running in a well bore by installing the float valve in a float body or bored-out drill collar of a tubular string. The float body may be positioned between two joints in a tubular string and is conventionally connected to the tubular string with conventional oilfield tubular threads such as a threaded box and pin connections for sealing engagement with conventional oil field tubular threads. When the float valve is positioned within the float body, seals provided on the exterior of the float valve body engage against the interior surfaces of the float body and provide a seal against high and low pressure fluids passing between the float body and the exterior of the float valve. Once the seal between float body and the exterior of the float valve is sealed all fluids are then flowed through the float valve and controlled by the float valve.
Fluid flow through a float valve body is controlled by the pressure of the fluid being flowed against a valve member positioned within the float valve body which overcomes the valve member's sealed and seated relationship against the seat on the interior surface of the float valve body which is created by the biased engagement of a spring against the valve member. While a float valve is necessary to control backflow from within the well and allow down flow of fluids being flowed from above, a float valve also is a restriction to flow in the profile between the valve member seat and the angular seat in the interior of the float valve body even when the float valve is fully open. This restrictive flow profile can have an affect on the functionality of the drilling operation and can create wear on those parts exposed to flow. Also the flow profile opening, between the valve member seat and the angular seat of the float body, can create turbulence in the fluid passing through which can cause vibration in the moving parts of the float valve. Further vibration and turbulence in the presence of drilling fluids, which contain drilling muds, chemicals, drill cuttings, glass or other kinds of beads, etc. can have abrasive affects on the valve member at the edges of its seating surfaces and on the stem of the valve member and on the spring for creating excessive wear which leads to a short life and ultimate failure of the float valve. Also the drilling fluids can, because of their small particle size, become jammed between the moving surfaces of the valve member stem and its supporting structure within the float valve body to create problems. Also this turbulence interferes with the smooth fluid flow of the drilling fluid to the drill bit or other piece of equipment in the drill string and therefore it is desirable to have a smooth flow and as large a volume of flow as possible through a float valve.
The prior art float valves have included a unitary valve member which was cast in one piece and included both the stem and valve member head, which engaged the valve seat located in the interior of the float valve body. Due to the exotic surfaces necessary to form a seal and the high cost of manufacturing this unitary valve element, two-piece valve elements are more commonly used in float valves and joined together at their stem and valve member head by conventional means. Various means of joining the two-piece, stem and valve member head, have been used including inertia welding and other mechanical interconnectors. Even exotic special means of connection were used such as using a shrink fit operation where the valve member head/cone includes a cylindrical shaped recess for receiving a front end of the stem during the shrink fit operation, wherein the valve member head/cone is heated relative to the stem, and the stem is impressed into the cylindrical recess for union and then both are air cooled for connection. This fitting or union is subject to being damaged in drilling operations because of the elevated downhole temperatures and due to vibrations to which the valve stem and valve member head/cone are subjected, specially in lateral well forces.
The float valve bodies, into which the valve members are inserted, are today cast as a single piece unit which creates problems with assembly. Assembling such cast valves bodies requires a window in the casting to allow for the insertion and manipulation of the valve member head with its valve stem and spring into the float valve body through the window. To achieve this large clearances must be allowed for such awkward installation which often results in wobble or deviation of the valve member head and its stem within the float valve body, thereby resulting in excessive wear on the valve member head and its stem and the valve stem bearing/bushing which shorten the life of the float valve. The wobbles and deviations of the valve member head and it's stem within a float valve bodies cast as a single piece are even greater and more likely to cause failure in an horizontal wells because of gravitational forces being perpendicular to the stem and valve member head.
The prior art float valves have also tended to use elastomeric seals and valve bushings with valve member heads to affect sealing engagement and allow smooth movement of the stem within the float valve between its open and closed positions. The prior art float valves using elastomeric seals tended to use large angles for the valve member head seats which were 45° to 90° and greater, because the valve head seats were not the primary source of sealing engagement but were used in conjunction with the elastomeric seal to form the seal between valve member head and the seat of the float valve body. This arrangement formed a good seal, but as the elastomeric seals wore down from operation in the abrasive environment of drilling fluids, these prior art float valves had a shorter life and were subject to catastrophic failure. The other soft spot for failure in the prior art float valves was at the valve bushing into which the stem of the valve member head was mounted to provide a smooth surface on which to slide back and forth in the operation of opening and closing the float valve. In the current drilling fluid environment these valve bushings/bearing were rapidly destroyed by the drilling fluids and thus left the stem of the valve member head loose in its mounting which allowed wobble in the valve member head and caused early failure of the float valve. This problem is especially acute in lateral wells because of the gravitational force being perpendicular to the stem of the valve head member versus being in alignment with the gravitational forces in vertical wells.
The prior art tended to focus on creating a reliable float valve, but did not focus as much on the flow profile of the opening between the valve head member and its seat on the inside of the float valve body and the flow passage through the rest of the float valve body where the stem of the valve head member and supporting structure were located to create smooth non-turbulent flow through the float valve. Thus the prior art provided seating surfaces on the valve head member which were 45° to 90° or greater angles through the line of the flow and thus seating surface on the interior of the valve body tended to be a problem. These angles for the seating surfaces tended to push the drilling fluid out of its normal path of flow and create excess turbulence at that point of flow in the valve body. In addition, the prior art did not provide for any cover or protection of the spring member and stem to the corrosive and abrasive fluid turbulence created by the seating surfaces on the valve head member just behind the valve member head where the spring and stem were located thereby exposing them to excessive wear which caused early failure in float valves. Also the prior art stems were generally cylindrical rods mounted in a sleeve bearing/bushing which was mounted in a supporting structure within the flow way of the lower half of the valve body to support the stem for smooth and even movement in and out as the float valve was operated. The cylindrical rods and support structure for them with sleeve bearings/bushing took up a great deal of cross-sectional area in the float valve body and restricted flow and positioned the sleeve bearing/bushing directly in line with corrosive and abrasive turbulent flow of the drilling fluid causing early failure in the float valve. These failures occurred in many ways, but in at least one way, as the drilling fluids destroyed the sleeve bearing/bushing it began to open up crevices which allowed the drilling fluids and their small particles to be jammed in between the stem and sleeve bearing/bushing not only causing additional wear but in some instances prevented the stem from sliding in and out in the sleeve bearing/bushing causing failure of the float valve.
Those skilled in the art would recognize that failure of a float valve can have significant adverse consequences, because any failed piece of equipment in a drill string requires a trip out and back in to the well which interferes with drilling operations. The prior art float valves were treated as separate units apart from sub joint strainers or X-collar filters which were used apart from the float valves to stop foreign particles in the drilling fluid from being jammed into the float valves or other operational equipment below and could not and did not function in direct relationship with a float valve or could be landed and be seated on a float valve because the float valve were not built to receive such filters and strainers.